edge_iterator_constructor.cpp

//=======================================================================
// Copyright 1997, 1998, 1999, 2000 University of Notre Dame.
// Authors: Andrew Lumsdaine, Lie-Quan Lee, Jeremy G. Siek
//
// Distributed under the Boost Software License, Version 1.0. (See
// accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)
//=======================================================================

/*
  Sample data (edge_iterator_constructor.dat):
  5
  10
  0 1
  1 2
  1 3
  2 4
  3 4
  1 0
  2 1
  3 1
  4 2
  4 3

  Sample output:

  0 --> 1
  1 --> 2 3 0
  2 --> 4 1
  3 --> 4 1
  4 --> 2 3

 */

#include <boost/config.hpp>
#include <utility>
#include <iostream>
#include <fstream>

#include <iterator>
#include <boost/graph/graph_utility.hpp>
#include <boost/graph/adjacency_list.hpp>

class edge_stream_iterator
{
public:
    typedef std::input_iterator_tag iterator_category;
    typedef std::pair< int, int > value_type;
    typedef std::ptrdiff_t difference_type;
    typedef const value_type* pointer;
    typedef const value_type& reference;

    edge_stream_iterator() : m_stream(0), m_end_marker(false) {}
    edge_stream_iterator(std::istream& s) : m_stream(&s) { m_read(); }
    reference operator*() const { return m_edge; }
    edge_stream_iterator& operator++()
    {
        m_read();
        return *this;
    }
    edge_stream_iterator operator++(int)
    {
        edge_stream_iterator tmp = *this;
        m_read();
        return tmp;
    }

protected:
    std::istream* m_stream;
    value_type m_edge;
    bool m_end_marker;
    void m_read()
    {
        m_end_marker = (*m_stream) ? true : false;
        if (m_end_marker)
        {
            *m_stream >> m_edge.first >> m_edge.second;
        }
        m_end_marker = (*m_stream) ? true : false;
    }
    friend bool operator==(
        const edge_stream_iterator& x, const edge_stream_iterator& y);
};
bool operator==(const edge_stream_iterator& x, const edge_stream_iterator& y)
{
    return (x.m_stream == y.m_stream && x.m_end_marker == y.m_end_marker)
        || (x.m_end_marker == false && y.m_end_marker == false);
}
bool operator!=(const edge_stream_iterator& x, const edge_stream_iterator& y)
{
    return !(x == y);
}

int main(int argc, const char** argv)
{
    typedef boost::adjacency_list<> IteratorConstructibleGraph;
    typedef boost::graph_traits< IteratorConstructibleGraph > Traits;
    Traits::vertices_size_type size_V;
    Traits::edges_size_type size_E;

    std::ifstream f(argc >= 2 ? argv[1] : "edge_iterator_constructor.dat");
    f >> size_V >> size_E;

    edge_stream_iterator edge_iter(f), end;
#if defined(BOOST_MSVC) && BOOST_MSVC <= 1300
    // VC++ can't handle the iterator constructor
    IteratorConstructibleGraph G(size_V);
    while (edge_iter != end)
    {
        int i, j;
        boost::tie(i, j) = *edge_iter++;
        boost::add_edge(i, j, G);
    }
#else
    IteratorConstructibleGraph G(edge_iter, end, size_V);
#endif
    boost::print_graph(G);

    return 0;
}